Some people with severe physical disabilities or serious neurological diseases that result in muscle weakness such as Lou Gehrig's disease (ALS) may have only one or two specific movements or muscles that they can readily control. Input devices have been developed to allow such people to control everything from a motorized wheelchair to a computer program. For example, besides hand operated input devices, there are input devices that can be activated by an eyelid blinking, or by puffing on a straw-like object. Using these input devices along with a scanning device, an individual may be able to select from a plurality of operation options. For example, the scanning device will scan through possible drive operation options one at a time, and indicates or identifies the nature of each choice to the user by highlighting it on a screen, by an audible tone, or by some other indicia appropriate to the user's abilities. The operation is highlighted for a predetermined amount of time, after which the scanning device automatically moves to the next operation option and highlights the next available operation option. After the desired operation option has been identified, the user may select the operation option by triggering the input device. In this way, a single switch input device may be used to operate a wheelchair.
Typical wheelchairs may have a four operation option scanning sequence (i.e. “Forward,” “Reverse,” “Left,” and “Right,” etc.) or even an eight operation option scanning sequence. When the scanning device reaches the chosen option the individual presses the input device and the chair drives in the direction chosen. Depending on the programmed scan timing and the number of available operation options (i.e. four or eight), the delay between the desire to place an input and availability of the input can be significant.